Re: [PATCH][PR gdb/18706] Calculate size of array of stubbed type

[Simon Marchi <simark@simark.ca>]

On 2020-04-27 7:41 a.m., Hannes Domani via Gdb-patches wrote:
> Sizes of stubbed types are calculated on demand in check_typedef, so the same
> must also be done for arrays of stubbed types.

For the uninitiated, can you please explain what's happening here, which types
are involved, which ones are stubs, and what that means.  That would help me
understand what happens here and be confident that the patch is correct.

> 
> gdb/ChangeLog:
> 
> 2020-04-27  Hannes Domani  <ssbssa@yahoo.de>
> 
> 	PR gdb/18706
> 	* gdbtypes.c (check_typedef): Calculate size of array of stubbed type.
> 
> gdb/testsuite/ChangeLog:
> 
> 2020-04-27  Hannes Domani  <ssbssa@yahoo.de>
> 
> 	PR gdb/18706
> 	* gdb.cp/stub-array-size.cc: New test.
> 	* gdb.cp/stub-array-size.exp: New file.
> 	* gdb.cp/stub-array-size.h: New test.
> 	* gdb.cp/stub-array-size2.cc: New test.
> ---
>  gdb/gdbtypes.c                           | 16 ++++++++++++++
>  gdb/testsuite/gdb.cp/stub-array-size.cc  | 25 ++++++++++++++++++++++
>  gdb/testsuite/gdb.cp/stub-array-size.exp | 27 ++++++++++++++++++++++++
>  gdb/testsuite/gdb.cp/stub-array-size.h   | 21 ++++++++++++++++++
>  gdb/testsuite/gdb.cp/stub-array-size2.cc | 22 +++++++++++++++++++
>  5 files changed, 111 insertions(+)
>  create mode 100644 gdb/testsuite/gdb.cp/stub-array-size.cc
>  create mode 100644 gdb/testsuite/gdb.cp/stub-array-size.exp
>  create mode 100644 gdb/testsuite/gdb.cp/stub-array-size.h
>  create mode 100644 gdb/testsuite/gdb.cp/stub-array-size2.cc
> 
> diff --git a/gdb/gdbtypes.c b/gdb/gdbtypes.c
> index 157b3c5e61..5e9de2ccb1 100644
> --- a/gdb/gdbtypes.c
> +++ b/gdb/gdbtypes.c
> @@ -2637,6 +2637,22 @@ check_typedef (struct type *type)
>  	  TYPE_LENGTH (type) = TYPE_LENGTH (target_type);
>  	  TYPE_TARGET_STUB (type) = 0;
>  	}
> +      else if (TYPE_CODE (type) == TYPE_CODE_ARRAY
> +	       && TYPE_NFIELDS (type) == 1)

Why is the `TYPE_NFIELDS (type) == 1` check necessary here?

> +	{
> +	  struct type *range_type = check_typedef (TYPE_INDEX_TYPE (type));
> +	  if (TYPE_CODE (range_type) == TYPE_CODE_RANGE
> +	      && has_static_range (TYPE_RANGE_DATA (range_type)))

Is it possible to have an array type where the index type is not TYPE_CODE_RANGE?

If it is not, then we should assert `TYPE_CODE (range_type) == TYPE_CODE_RANGE`.  If it
can be of another type, what are the other possibilities?

> diff --git a/gdb/testsuite/gdb.cp/stub-array-size.exp b/gdb/testsuite/gdb.cp/stub-array-size.exp
> new file mode 100644
> index 0000000000..cb486cd459
> --- /dev/null
> +++ b/gdb/testsuite/gdb.cp/stub-array-size.exp
> @@ -0,0 +1,27 @@
> +# Copyright 2020 Free Software Foundation, Inc.
> +#
> +# This program is free software; you can redistribute it and/or modify
> +# it under the terms of the GNU General Public License as published by
> +# the Free Software Foundation; either version 3 of the License, or
> +# (at your option) any later version.
> +#
> +# This program is distributed in the hope that it will be useful,
> +# but WITHOUT ANY WARRANTY; without even the implied warranty of
> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> +# GNU General Public License for more details.
> +#
> +# You should have received a copy of the GNU General Public License
> +# along with this program.  If not, see <http://www.gnu.org/licenses/>.
> +
> +# This file is part of the gdb testsuite.

Please add a short introductory comment that explains what this intends to test.

Simon